1. Field of the Invention
The present invention relates to a testing system, more specifically to a testing system for testing semiconductor devices, a testing method for testing semiconductor devices, and a method for manufacturing semiconductor devices.
2. Description of the Related Art
A semiconductor device is manufactured by a series of processes including a combination of lithography, etching, heat treatment (oxidation, annealing, or diffusion), ion implantation, thin film formation (CVD, sputtering, or vapor deposition), washing (resist removal or washing with a solution), or the like. After the treatment of each process, testing is carried out to check adequacy of the treatment, magnitude of variation, and the like. For example, in the lithography process to transfer an image of a mask pattern to a working wafer, dimensional measurement of the transferred pattern is performed.
In the testing process, sampling test is performed. Specifically, in a lot including a plurality of semiconductor wafers, some semiconductor wafers are sampled and then tested. Results of the testing are considered as representative values of the lot. The sampling test in the testing process is to save time and effort required for the 100-percent-testing. However, along with a recent increase in integration of semiconductor devices, each process becomes difficult to control, and the number of items to be tested is getting larger than before. For example, the dimensional measurement after the lithography requires monitoring of variation in a shot, variation between shots, variation between wafers, and the like.
In currently-available method of testing, areas to be tested are previously decided. Accordingly, it is difficult to cover all the test items within the limited number of tests. For example, when the number of testing points determined on a throughput of a testing apparatus or costs is limited to 30 points, the test items are determined as: five points per shot, six shots per wafer, and one wafer per lot. The variation in a shot and variation between shots, for which many tests are carried out, can be monitored. However, the variation between wafers cannot be monitored since only one wafer is measured. However, since wafers are varied, the representative values of the lot cannot be properly calculated by sampling only one wafer from the lot.